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net: add skb_frag_foreach_page and use with kmap_atomic

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Skb frags may contain compound pages. Various operations map frags
temporarily using kmap_atomic, but this function works on single
pages, not whole compound pages. The distinction is only relevant
for high mem pages that require temporary mappings.

Introduce a looping mechanism that for compound highmem pages maps
one page at a time, does not change behavior on other pages.
Use the loop in the kmap_atomic callers in net/core/skbuff.c.

Verified by triggering skb_copy_bits with

    tcpdump -n -c 100 -i ${DEV} -w /dev/null &
    netperf -t TCP_STREAM -H ${HOST}

  and by triggering __skb_checksum with

    ethtool -K ${DEV} tx off

  repeated the tests with looping on a non-highmem platform
  (x86_64) by making skb_frag_must_loop always return true.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn
2017-07-31 08:15:47 -04:00
committed by David S. Miller
parent 1ae39d658d
commit c613c209c3
2 changed files with 95 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

88
net/core/skbuff.c
View File

@@ -938,8 +938,10 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
struct ubuf_info *uarg = skb_shinfo(skb)->destructor_arg;
for (i = 0; i < num_frags; i++) {
u8 *vaddr;
skb_frag_t *f = &skb_shinfo(skb)->frags[i];
u32 p_off, p_len, copied;
struct page *p;
u8 *vaddr;
page = alloc_page(gfp_mask);
if (!page) {
@@ -950,10 +952,15 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
}
return -ENOMEM;
}
vaddr = kmap_atomic(skb_frag_page(f));
memcpy(page_address(page),
vaddr + f->page_offset, skb_frag_size(f));
kunmap_atomic(vaddr);
skb_frag_foreach_page(f, f->page_offset, skb_frag_size(f),
p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
memcpy(page_address(page) + copied, vaddr + p_off,
p_len);
kunmap_atomic(vaddr);
}
set_page_private(page, (unsigned long)head);
head = page;
}
@@ -1753,16 +1760,20 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
end = start + skb_frag_size(f);
if ((copy = end - offset) > 0) {
u32 p_off, p_len, copied;
struct page *p;
u8 *vaddr;
if (copy > len)
copy = len;
vaddr = kmap_atomic(skb_frag_page(f));
memcpy(to,
vaddr + f->page_offset + offset - start,
copy);
kunmap_atomic(vaddr);
skb_frag_foreach_page(f,
f->page_offset + offset - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
memcpy(to + copied, vaddr + p_off, p_len);
kunmap_atomic(vaddr);
}
if ((len -= copy) == 0)
return 0;
@@ -2122,15 +2133,20 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len)
end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
u32 p_off, p_len, copied;
struct page *p;
u8 *vaddr;
if (copy > len)
copy = len;
vaddr = kmap_atomic(skb_frag_page(frag));
memcpy(vaddr + frag->page_offset + offset - start,
from, copy);
kunmap_atomic(vaddr);
skb_frag_foreach_page(frag,
frag->page_offset + offset - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
memcpy(vaddr + p_off, from + copied, p_len);
kunmap_atomic(vaddr);
}
if ((len -= copy) == 0)
return 0;
@@ -2195,20 +2211,27 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
u32 p_off, p_len, copied;
struct page *p;
__wsum csum2;
u8 *vaddr;
if (copy > len)
copy = len;
vaddr = kmap_atomic(skb_frag_page(frag));
csum2 = ops->update(vaddr + frag->page_offset +
offset - start, copy, 0);
kunmap_atomic(vaddr);
csum = ops->combine(csum, csum2, pos, copy);
skb_frag_foreach_page(frag,
frag->page_offset + offset - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
csum2 = ops->update(vaddr + p_off, p_len, 0);
kunmap_atomic(vaddr);
csum = ops->combine(csum, csum2, pos, p_len);
pos += p_len;
}
if (!(len -= copy))
return csum;
offset += copy;
pos += copy;
}
start = end;
}
@@ -2281,24 +2304,31 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
u32 p_off, p_len, copied;
struct page *p;
__wsum csum2;
u8 *vaddr;
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
if (copy > len)
copy = len;
vaddr = kmap_atomic(skb_frag_page(frag));
csum2 = csum_partial_copy_nocheck(vaddr +
frag->page_offset +
offset - start, to,
copy, 0);
kunmap_atomic(vaddr);
csum = csum_block_add(csum, csum2, pos);
skb_frag_foreach_page(frag,
frag->page_offset + offset - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
csum2 = csum_partial_copy_nocheck(vaddr + p_off,
to + copied,
p_len, 0);
kunmap_atomic(vaddr);
csum = csum_block_add(csum, csum2, pos);
pos += p_len;
}
if (!(len -= copy))
return csum;
offset += copy;
to += copy;
pos += copy;
}
start = end;
}